With the rapid development of railway transportation of People's Republic of China (PRC), the railway transportation mode with characteristics of large capacity, high axle load and high density has been initially formed. Under the increasingly harsh conditions of rail track, the damage problem of steel rails and turnout tracks of railway is increasingly prominent. Turnout tracks are not only important equipment for performing railway connection and crossing, but also one of key links affecting operational efficiency and traffic safety of railways.
At present, turnout tracks are processed with a mode that steel rail manufacturers provide raw materials and the turnout truck manufacturers carry out milling process and subsequent treatments. Generally, the strength and hardness of hot-rolled turnout tracks are relatively low, the turnout tracks are prone to generate harmful defects such as stripping and falling-off, and rapid abrasion, particularly under the impact of impulsive load of heavy haul train. Therefore, the processed turnout tracks are required to conduct heat treatment, so as to improve the overall performance of turnout track and extending its service life. However, due to a mode of processing firstly and heat treatment is then applied, the steel rails are anew experienced with austenization and cooling process, its mechanical parameters (e.g., straightness) are difficult to meet the higher requirements, thereby limiting the applications of turnout tracks in the high-speed and quasi-high-speed rail lines. Meanwhile, the depth of the hardened layer of railhead is limited under an off-line heating condition, the depth is usually less than 15 mm, while the maximum processing depth of turnout split reaches 23 mm, the hardening effect is difficult to be effectively utilized, thereby affect the service life of turnout tracks.
In recent years, the evolution of on-line heat treatment technology for steel rails provides fresh ideas for heat treatment of turnout track as follows: by imposing cooling medium to railhead and other parts of steel rails having residual heat following a hot-rolling process, can obtain the turnout tracks with significantly improved performances as compared with those in a hot-rolled state.